Photolithographic process for producing etched patterns on the surface of fine tubes, wires or other three dimensional structures

Abstract

The present invention involves a photolithographic process, and apparatus and material for use therein, for producing etched or eroded areas or holes in a selected pattern on or in the surface of fine workpieces, such as small diameter tubes. One aspect of the present invention is a photolithographic process for producing a selected pattern on a nonplanar surface of a workpiece using at least one mask to define the selected pattern. The process includes the acts of applying a photoresist material to the workpiece and aligning the mask with the nonplanar surface of the workpiece. The mask may have an inner surface that corresponds to the nonplanar surface. The process may also include the acts of exposing and developing the photoresist material.

We claim:  
     
       1. A photolithographic process for producing a selected pattern on a nonplanar surface of a workpiece using at least one rigid mask shaped complimentary to the nonplanar surface to define the selected pattern, comprising: 
       a) applying a photoresist material to the workpiece; and  
       b) aligning the mask and the nonplanar surface of the workpiece.  
     
     
       2. The method of  claim 1 , wherein the mask has a first surface that corresponds to the nonplanar surface. 
     
     
       3. The method of  claim 1 , further comprising: 
       exposing and developing the photoresist material.  
     
     
       4. The method of  claim 1 , further comprising: 
       cleaning the nonplanar surface with a detergent; and  
       rinsing the nonplanar surface with deionized water.  
     
     
       5. The method of  claim 1 , further comprising: 
       baking the workpiece and the photoresist material in an oven.  
     
     
       6. The method of  claim 1 , where in the act of developing the photoresist material comprises: 
       immersing the photoresist material in a developer solution.  
     
     
       7. The method of  claim 1 , further comprising: 
       developing the exposed photoresist material to uncover a portion of the workpiece; and  
       etching the exposed portion of the workpiece.  
     
     
       8. The method of  claim 7 , wherein the act of etching the exposed portion of the workpiece comprises: 
       immersing the workpiece in a chemical etchant.  
     
     
       9. The method of  claim 7 , wherein the act of etching the exposed portion of the workpiece comprises: 
       placing the workpiece in a plasma.  
     
     
       10. The method of  claim 1 , wherein the workpiece is metallic. 
     
     
       11. The method of  claim 1 , wherein the workpiece is nitinol. 
     
     
       12. The method of  claim 1 , wherein the workpiece is cylindrical. 
     
     
       13. The method of  claim 1 , wherein the workpiece defines an interior lumen. 
     
     
       14. The method of  claim 13 , further comprising: 
       plugging the interior lumen with a plug.  
     
     
       15. The method of  claim 14 , wherein the plug comprises platinum. 
     
     
       16. The method of  claim 14 , wherein the plug comprises stainless steel. 
     
     
       17. The method of  claim 14 , wherein the interior lumen is cylindrical and wherein the plug is a wire. 
     
     
       18. The method of  claim 1 , further comprising: 
       exposing a first portion of the photoresist material;  
       rotating the workpiece relative to the mask; and  
       exposing a second portion of the photoresist material.  
     
     
       19. The method of  claim 18 , further comprising: 
       providing a radial alignment indicator; and  
       using the radial alignment indicator to radially position the workpiece.  
     
     
       20. The method of  claim 19 , wherein the radial alignment indicator serves as a plug to minimize the intrusion of process chemicals into an interior opening of the workpiece. 
     
     
       21. The method of  claim 1 , further comprising: 
       providing a fixture adapted to allow observation of the relative radial location of the workpiece and the mask.  
     
     
       22. The method of  claim 21 , wherein the workpiece is a cylindrical and wherein the mask is a hemicylinder. 
     
     
       23. The method of  claim 1 , wherein the mask comprises a material chosen from the group consisting of stainless steel, aluminum, brass, and bronze. 
     
     
       24. The method of  claim 1 , wherein the mask defines a plurality of apertures. 
     
     
       25. The method of  claim 24 , wherein the apertures are substantially rectangular. 
     
     
       26. The method of  claim 24 , wherein the apertures are substantially oval in shape. 
     
     
       27. The method of  claim 24 , wherein a first portion of the apertures are substantially rectangular and wherein a second portion of the apertures are substantially oval in shape. 
     
     
       28. The method of  claim 1 , wherein the mask has a smooth interior surface. 
     
     
       29. The method of  claim 1 , further comprising: 
       providing a first stop and a second stop jogging the workpiece against the first stop;  
       rotating the workpiece; and  
       jogging the workpiece against the second stop.  
     
     
       30. The method of  claim 29 , further comprising: 
       machining an alignment notch into the workpiece, the alignment notch adapted to receive the first stop.  
     
     
       31. The method of  claim 1 , wherein the selected pattern comprises a plurality of opposed, offset areas. 
     
     
       32. A method of forming a selected pattern on a nonplanar surface, comprising: 
       a) providing a workpiece having a nonplanar surface;  
       b) applying a photoresist layer over the nonplanar surface;  
       c) providing a rigid mask that corresponds to the nonplanar surface, the mask defining an aperture;  
       d) aligning the mask over the nonplanar surface;  
       e) shining a light through the aperture, thereby exposing a first portion of the photoresist layer;  
       f) rotating the workpiece relative to the rigid mask;  
       g) shining the light through the aperture, thereby exposing a second portion of the photoresist layer.  
     
     
       33. The method of  claim 32 , further comprising: 
       repeating the acts of rotating the workpiece relative to the mask and shining the light through the aperture, thereby exposing at least one additional portion of the photoresist layer.  
     
     
       34. A photolithographic method of forming a radially spaced offset pattern on a three dimensional workpiece, comprising: 
       a) placing a workpiece on a stage, the workpiece having a photo-sensitive coating;  
       b) jogging the workpiece against a first stop;  
       c) exposing a first portion of the photo-sensitive coating through a rigid mask shaped complementary to the nonplanar surface;  
       d) rotating the workpiece;  
       e) jogging the workpiece against a second stop; and  
       f) exposing a second portion of the photo-sensitive coating though the mask.  
     
     
       35. The photolithographic method of  claim 34 , further comprising: 
       repeating the acts of rotating and jogging to obtain a circumferential pattern around the workpiece.